A group signature mechanism, which is one of the very important cryptographic authentication mechanisms for protecting user's privacy, has been widely researched and has been considerably developed since the concept thereof is first proposed by Chaum and Heyst in 1991. Various security requirements, formal models, and detailed mechanisms have been proposed. Recently, a group signature mechanism providing controllable linkability by extending typical group signature mechanisms has been researched.
Typical authentication mechanisms, such as an ID/password authentication mechanism, a real-name based PKI authentication mechanism, and an i-Pin mechanism, and the like, have many disadvantages, such as personal information exposure due to a registration and identification process of personal information, leakage due to excessive personal information collection and management carelessness of a service provider, a wide range of activity trace, and the like. As a result, a group signature mechanism providing controllable linkability as an effective anonymous authentication mechanism that can replace the above-mentioned mechanisms has been actively researched recently.
The group signature mechanism providing controllable linkability additionally has controllable linkability capable of identifying that group signatures are linked with each other (that is, the group signatures are generated by one signer or a signer key) when a special linking key is provided, by extending the typical group signature mechanisms simply handling anonymity using a dichotomical structure that conceals/recovers identity information or ID of a signer. Therefore, the anonymity can be controlled to various levels according to the desired policy.
Using the characteristics, a service provider can obtain user related effective information from various anonymity based services, for example, web based personalized anonymous authentication service or in the case of data mining, anonymous authentication data, while maintaining anonymity of identity information.
Existing group signature mechanisms providing various security characteristics such as the known controllable linkability, and the like, cannot be widely adopted in various application environments due to structural complexity. Currently, user storage costs and operation costs are very cheap. Therefore, costs of resources for designing the system greatly depends on communication costs and therefore, the group signature mechanism providing controllable linkability with short signatures is urgently required in low resource application environments such as a radio Internet based service market.
Recently, application mechanisms for enhancing privacy protection by performing anonymous authentication between the smart terminals by using short range communication environment, and the like, have been researched and developed.
As an example, a method for transmitting information using multi-dimensional codes such as a QR code has been greatly interested as one method of short range communications. A device with a built-in camera capable of recognizing the multi-dimensional code can obtain information through the multi-dimensional codes any time and therefore, the user can process information using the corresponding devices without separate communication networks (thus, without charging communication costs). The method for recognizing multi-dimensional codes through a camera is performed by a contactless type and therefore, does not require devices such as a separate connection cable, and the like.